1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to image encoding and decoding, and more particularly, to image encoding/decoding in which one of a plurality of color component images of an image is predicted from a different color component image using a correlation between the color component images, thereby improving encoding efficiency.
2. Description of the Related Art
In general, when an image is captured, the captured original image is in a red, green, and blue (RGB) color format. To encode the RGB color format image, the RGB color format image is transformed into a YUV (or YCbCr) color format. Y is a black-white image and has a luminance component, and U (or Cb) and V (or Cr) have color components. Information is uniformly distributed over R, G, and B in an RGB image, but information is concentrated in Y and the amount of information in U (or Cb) and V (or Cr) is small in a YUV (or YCbCr) image. Thus, the YUV (or YCbCr) image can be compressed with high compression efficiency. To further improve compression efficiency, an YUV (or YCbCr) 4:2:0 image obtained by sampling color components U (or Cb) and V (or Cr) of an YUV (or YCbCr) image at a ratio of 1:4 is generally used.
However, since ¼ sampling of U (or Cb) and V (or Cr) in the YUV (or YCbCr) 4:2:0 image causes color distortion, it is not suitable for providing high display quality. Thus, a method for effectively encoding a YUV (or YCbCr) 4:4:4 image without sampling U (or Cb) and V (or Cr) is required. Recently, residual color transform (RCT), which directly encodes an RGB 4:4:4 image to remove color distortion occurring in transformation of an RGB image to a YUV (or YCbCr) image, has been suggested.
When an image like a YUV (or YCbCr) 4:4:4 image and an RGB 4:4:4 image, in which color components have the same resolution, is directly encoded using a related art encoding method, encoding efficiency is degraded. Thus, a method for improving encoding efficiency while maintaining high display quality by prediction based on the statistical characteristics of an image is required for a case where a YUV (or YCbCr) 4:4:4 image is encoded or an RGB image is encoded in an RGB domain without being transformed to a YUV (or YCbCr) format.